Apple tree rootstock named &#39;G.890&#39;

ABSTRACT

The present invention relates to a new and distinct variety of apple tree rootstock named ‘G.890.’ The ‘G.890’ apple tree rootstock is a dwarfing rootstock that is resistant to fire blight ( Erwinia amylovora ) and crown rot ( Phytophthora cactorum ). The ‘G.890’ rootstock is useful in that it can be propagated clonally and used as a rootstock or root system for apple trees as well as for interstems of apple trees.

STATEMENT REGARDING FEDERAL FUNDING

Research related to this invention was funded under USDA ARS CRADA,Sponsor's Contract #: 58-3K95-9-1358-M; the U.S. government may haverights herein.

CROSS REFERENCE TO RELATED APPLICATIONS

Not applicable.

GENUS AND SPECIES

Malus domestica×Malus robusta hybrid

VARIETY DENOMINATION

‘G.890’

BACKGROUND OF THE INVENTION I. Field & Utility Summary

The present invention relates to a new and distinct variety of appletree rootstock. The rootstock is useful in that it can be propagatedclonally and used as a rootstock or root system for apple trees as wellas for interstems of apple trees.

II. Cultivation Summary

‘G.890’ originated from a planned cross in 1976 in Geneva, N.Y.

III. Characteristics Summary

The ‘G.890’ apple tree rootstock is a dwarfing rootstock that isresistant to fire blight (Erwinia amylovora) and crown rot (Phytophthoracactorum). While ‘G.890’ rootstock is a hybrid from a cross between‘Ottawa 3’ and ‘Robusta 5’, it is distinct from its parent cultivars interms of dwarfing. The apple tree rootstock ‘G.890’ is less dwarfingthan ‘Ottawa 3’ and more dwarfing than the non-dwarfing parent ‘Robusta5’. Unlike ‘Ottawa 3’, ‘G.890’ is resistant to fire blight. Although‘G.890’ is in the same dwarfing market class as ‘M.7’, and ‘MM.106’ itis distinguishable from ‘M.7’ and ‘MM-106’ because ‘G.890’ is resistantto fire blight whereas ‘M.7’ and ‘MM-106’ are susceptible. It is alsodistinguishable from ‘M.7’ and ‘MM.106’ because it is tolerant to thebiotic replant disease complex whereas ‘M.7’ and ‘MM-106’ are not.

IV. Breeding History

In the spring of 1976, pollen from a Malus robusta ‘Robusta 5’ appletree was applied to emasculated flowers of a Malus domestica ‘Ottawa 3’apple tree at the New York State Agricultural Experiment Station(“NYSAES”), Cornell University, Geneva, N.Y. In the fall of 1976,approximately 500 seeds resulting from this pollination were extractedfrom mature fruit derived from this cross. In the winter of 1976-77, theseeds were stratified and planted in large flats under conditionseffective to germinate seeds and obtain seedlings. When germinatedseedlings were about 2.5 cm tall they were inoculated with a mixture ofisolates of the fungus Phytophthora cactorum (the causal agent of crownand root rots). The flats were flooded to mid-hypocotyl level and keptat 23° C. for one week. Surviving seedlings were transplanted intoindividual pots.

In the summer of 1977, each of the transplanted seedlings was inoculatedwith approximately 10⁶ colony forming units of the Ea 273 strain of thefire blight bacterium Erwinia amylovora by inserting a 26-gaugehypodermic syringe needle into the shoot tip. The seedling designated as#890 was one of the survivors of this battery of inoculations from thesame cross. All the surviving plants were transplanted to the Loomisfield (NYSAES, Cornell University, Geneva, N.Y.) in the fall of 1977 andallowed to grow side shoots for propagation/evaluation. In 1980, ‘G.890’was evaluated for rooting ability, lack of spine production, and lowroot brittleness in a layering bed (stool bed). In 1983, 4 finishedtrees with ‘G.890’ rootstock were planted in a first test orchard on theLoomis farm (NYSAES, Cornell University, Geneva, N.Y.) with Malusdomestica cv. ‘Golden Delicious’ grafted onto this rootstock as thescion cultivar. This rootstock performed well (top 20% of manyrootstocks tested) in these first test trials. In the Spring of 2002G.890 and other experimental rootstocks were planted as finished treeswith two scion varieties on the Research South farm (NYASES, GenevaN.Y.) and in 2003 and 2004 the orchard was spray inoculated while inbloom with fire blight and all trees of G.890 survived indicating goodresistance of the rootstock in an orchard environment. In August 2002,several rootstock liners of ‘G.890’ were budded with 15 different scioncultivars to test graft union compatibility—the test results showed that‘G.890’ was compatible with all the cultivars tested. In summer 2007, 20rootstock liners were inoculated with two different strains of fireblight (ten liners per strain) in the Plant Genetic Resources Unitgreenhouse (NYSAES, Cornell University, Geneva, N.Y.) of the U.S.Department of Agriculture Agricultural Research Service. As a result,the apple rootstock ‘G.890’ was classified as immune to one of thestrains tested and less resistant to the other strain of fire blight. Inthe fall of 2005 and 2006 the inventors measured tree architecture ofnursery trees on G.890 and found that it promotes a spreading habit(flatter branches) on three diverse grafted scion varieties.

V. Asexual Reproduction

Asexual reproduction of the ‘G.890’ apple rootstock has been achievedusing the traditional method of clonally propagating apple rootstocks.In particular, the original seedling of the ‘G.890’ apple rootstock wasplanted in the Loomis field (NYSAES, Cornell University, Geneva, N.Y.)and allowed to develop into a “mother plant.” The ‘G.890’ mother plantwas then used to obtain rooted liners using conventional layeringprocedures. The resulting liners were then planted in a row to generatea layering stool bed (also referred to as the “mother stool bed”). Theliving tissues (i.e. leaves, stems, roots, buds, and spines) of themother stool bed were observed to be identical to secondary and tertiarystool bed plants. In addition to conventional layering, the ‘G.890’apple rootstock variety has been asexually reproduced by root cuttings,by budding and grafting onto seedling and clonal rootstocks, and bytissue culture.

VI. Stability

Observations of trees from these propagations indicate that all treeshave proven true to type and identical in all appearances to theoriginal tree.

VII. Detailed Comparisons

The seed parent Malus domestica ‘Ottawa 3’ is a dwarfing rootstock,i.e., trees grown on this rootstock are 30 to 35 percent the size of astandard self-rooted seedling tree. ‘Ottawa 3’ is known to induce goodprecocity to the scion (i.e., the ability to induce early reproductivedevelopment in the scion) and has high yield efficiency. ‘Ottawa 3’plants produce no spines, are fairly well anchored, are a very coldhardy rootstock and have resistance to crown and root rot caused byPhytophthora cactorum. However, ‘Ottawa 3’ is susceptible to the woollyapple aphid (Eriosoma lanigerum) and to fire blight (Erwinia amylovora).

The pollen parent Malus robusta ‘Robusta 5’ is a non-dwarfing rootstock,i.e. trees on this rootstock are the same size as a standard self-rootedtree. ‘Robusta 5’ does not induce precocity to the scion and is nothighly yield efficient. Juvenile plants of ‘Robusta 5’ produce manyspines. ‘Robusta 5’ breaks buds very early in the spring and is winterhardy. It is resistant to powdery mildew (Podosphaera leucotricha) andfire blight, and is immune to the woolly apple aphid. Further, ‘Robusta5’ has shown tolerance to the specific replant disease complex.

The ‘G.890’ apple rootstock of the present invention has a combinationof qualities that distinguishes it from its parental plants (i.e.,‘Ottawa 3’ and ‘Robusta 5’). For example, although ‘G.890’ has dwarfingproperties derived from ‘Ottawa 3’, it is different from its dwarfingparent (i.e., ‘Ottawa 3’) because it produces a tree that is 60 to 70percent of the size of a standard self-rooted seedling tree. Thus‘G.890’ belongs to a different dwarfing vigor class than its ‘Ottawa 3’parent. In particular, ‘G.890’ has dwarfing characteristics that areintermediate between the industry standards of Malus domestica ‘Malling7’ and Malus domestica ‘Malling-Merton 106’. ‘G.890’ shares similaritieswith ‘Ottawa 3’ in that they both induce precocity to the scion, areyield efficient, winter hardy, and resistant to crown and root rotcaused by Phytophthora cactorum.

With regard to its ‘Robusta 5’ parent, ‘G.890’ is distinguishable inthat it is a dwarfing rootstock and is highly yield efficient, while‘Robusta 5’ is not. However, like ‘Robusta 5’, ‘G.890’ is resistant tofire blight and possesses the genetic markers linked to the mainresistance to powdery mildew and has shown field resistance to powderymildew. In addition, ‘G.890’ has been shown to have some tolerance tothe replant disease complex.

As discussed above, ‘G.890’ is intermediate between ‘M.7’ and ‘MM.106’in terms of dwarfing class. However, ‘G.890’ is more precocious andyield efficient than ‘M.7’ and ‘MM.106’. ‘G.890’ is resistant to fireblight whereas ‘M.7’, ‘MM.106’ and other rootstocks in its market classare not.

VIII. Brief Description of the Figures

FIG. 1 shows budded liners in the nursery.

FIG. 2 live plants in a propagation bed.

FIG. 3 shows a close up of an actively growing shoot

FIG. 4 shows the adaxial (upper) lamina surface of a mature leaf.

FIG. 5 bark and leaves on an actively growing shoot.

IX. Detailed Botanical Description

The following description of apple tree rootstock ‘G.890’ containsreferences to color names taken from The Royal Horticultural SocietyColour Chart (R.H.S.), 2001 edition. Botanical descriptions follow theManual of Cultivated Plants (Bailey, 1949).

-   Tree:    -   -   Habit.—A self-rooted tree of ‘G.890’ is a small shrub            typically standing about 1.5-2 meters tall by about 2 meters            wide when 7 years old. There is no single dominant trunk.            Instead there are few shoots arising from the crown. Very            few suckers (i.e., new shoots emerging from below ground)            are produced. Liners planted in the nursery stop apical            growth mid season. The apical bud in these plants is            pubescent Greyed-Green (RHS 191D).        -   Productivity.—In an intermediate trial performed at the            NYSAES (Cornell University, Geneva, N.Y.), the ‘G.890’            rootstock received the cultivar ‘Empire’ (Malus domestica)            as the scion and was compared to the Malus domestica check            rootstocks M.9 EMLA, M.26 and M.7. ‘G.890’ was shown to have            statistically higher (p≦0.05) yield efficiency (kg yield/cm²            trunk cross sectional area) than all the check rootstocks.        -   Precocity.—Scion cultivars budded on ‘G.890’ exhibit the            same precocity as those budded on M.9.        -   Fertility (fecundity).—The ‘G.890’ plant produces flowers            and fruits regularly.-   Dormant shoots (buds and bark):    -   -   Dormant mature shoots.—Color: Greyed-Red (RHS 178A) where            exposed to full sunlight grading to Greyed-Orange (RHS 173B)            with diminished light exposure Texture: Very light            pubescence which gradually disappears in older tissues Size:            30-60 cm long; may have some spines.        -   Axillary buds.—Size: 2-3 mm long and 3 mm wide with little            pubescence. Shape: Obtuse, sessile, somewhat appressed and            flattened. Texture: Some pubescence.        -   Bark on three-year-old shoots.—Color: Greyed-Green (RHS            197A) Lenticels: Color: Greyed-Orange (RHS 163B) Size:            0.3-0.4 mm in diameter. Quantity: 1-2 lenticels per cm².-   Leaves:    -   -   Mature leaves.—Leaf arrangement: Alternate Shape: Simple,            recurved, oblong-ovate Size: Length: 85 mm Width: 50 mm at            the widest point Laminae: Somewhat wavy Apex: Acuminate            Base: Nearly symmetrical rounded Margin: Acutely serrated,            with about 5 serrations per cm Upper surface: Color: Green            (RHS 126B) Texture: Glabrous and translucent Lower surface:            Color: Green (RHS 146C) Texture: Somewhat pubescent            Venation: Netted Leaf poise: 15°-25° from the shoot,            depending on shoot orientation Stipules: Length: 8 mm Width:            2 mm Petioles: Diameter: 2 mm Color: Gradation of Green (RHS            140A) to Greyed-Red (RHS 179A) depending on low or high            exposure to light.-   Flowers: Because their primary use is for rootstocks, the plants of    G.890 have not been allowed to flower yet and therefore no flowers    have been observed yet.-   Fruit: Because their primary use is for rootstocks, the plants of    G.890 have not been allowed to set fruit yet and therefore no fruit    has been observed yet.-   Disease resistance: As described above, the ‘G.890’ rootstock of the    present invention exhibits resistance to fire blight. The percent    lesion measured after inoculation of potted liners in the greenhouse    using four different strains of E. amylovora was negligible for two    of the strains and moderate for the other two, indicating a specific    resistance to the bacterium. The ‘G.890’ rootstock, having survived    the inoculation with crown and root rot, is also considered    resistant to crown and root rots caused by Phytophthora cactorum.

1. A new and distinct variety of apple tree named ‘G.890’ hereindescribed and illustrated.